Coherence bandwidth adaptive CSI reporting

ABSTRACT

This disclosure pertains to a wireless device for a Radio Access Network, the wireless device being adapted for transmitting sampling information indicating a sample determining device used by the wireless device for preparing a measurement report. The disclosure also pertains to related methods and devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Submission Under 35 U.S.C. § 371 for U.S. NationalStage Patent Application of International Application Number:PCT/SE2016/050934, filed Sep. 30, 2016 entitled “COHERENCE BANDWIDTHADAPTIVE CSI REPORTING,” the entirety of which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure pertains to wireless communication technology, inparticular Radio Access Technology.

BACKGROUND

In many wireless communication networks, Downlink Reference Signals(DL-RSs) are used to enable the UE to estimate the DL channel and thenreport the obtained measurements to the base-station (CSI reporting).The CSI reporting can be done in multiple formats, for example, explicitchannel estimates, pre-coder information etc. The larger the antennaarrays become, the more the amount of feedback increases.

5G systems are expected to support larger and larger antenna arrays; upto 256 antennas should be supported according to current understandingin 3GPP.

This may lead to the amount of data in CSI reports for a large number ofantennas increasing, as the channel matrix scales with the product ofthe number of receiver antennas and the number of transmit antennas.Another issue may be that the estimation quality per antenna decreases,both due to the facts that high compression is needed in reports, andthat the available output power per antenna may decrease such that theper antenna estimation quality decreases, the estimation quality perantenna decreases, i.e. the information content per antenna maydecrease. Therefore, the demand for processing gain increases.

Another problem with current pre-coder procedures is that in many casesthe precoding is carried out block wise, e.g., a fixed pre-coder may beapplied for a group of N resource blocks, and then a new pre-coder isapplied for the next group of N resource blocks. This implies thatsudden changes in the effective channel (physical channel includingprecoding) may be present in between the blocks. These potentialdiscontinuities of the effective channel imply that the channelestimation on the receiver side needs to be done block-wise, whichimplies that the channel estimation suffers as it gets many edge-effectsand a limitation in the choices of filter for the receiver to use forgaining processing gain. Note that even if the actual effective channelis smooth across several groups of PRBs, due to low delay spread and thesame pre-coder being applied to several consecutive groups, the channelestimation is limited to the groups of N resource blocks. This isbecause the precoding operation is transparent to the receiver. Thisforces the receiver to be conservative in the sense that nointerpolation is performed across the aforementioned group of PRBs evenif the actual channel conditions would allow it.

Moreover, in order to achieve good CSI quality, a large number ofpre-coders need to be signaled to cover the entire band. This requires asignificant control channel capacity.

SUMMARY

It is an object of the present disclosure to provide approaches allowingimproved measurement report, respectively improvements related toreference signaling and/or processing of reference signaling.

There is disclosed a wireless device for a Radio Access Network. Thewireless device is adapted for transmitting sampling informationindicating a sample determining device used by the wireless device forpreparing a measurement report. The wireless device may comprise atransmitting module for such transmitting.

There is also disclosed a method for operating a wireless device in aRadio Access Network. The method comprises transmitting samplinginformation indicating a sample determining device used by the wirelessdevice for preparing a measurement report.

With transmitting the sampling information, another node of the network,e.g. a wireless precoding node, may be informed about the sampledetermining device used, such that it (or another node of the network),may adapt its own transmissions, in particular its precoding,accordingly. For example, if the precoding device knows (from theindication of the sample determining device) which frequencies thewireless device considers noise (because it filters them out, e.g. usinga low-pass filter as sampling determining device to filter out highfrequencies considered noise), it can adapt its precoder accordingly. Byproviding corresponding information, the wireless device facilitatesthis precoding.

The sampling information may explicitly or implicitly indicate thesampling determining device. For example, the information may beimplicit from the samples (and/or sample density, e.g. in frequencydomain, and/or frequency range covered by the samples) provided and/orincluded in the measurement report, e.g. based on assuming a specifictype of sampling determining device is used. For example, if a low-passfilter, respectively a SINC or windowed SINC, type filter is used, thesample determining device may be indicated by the samples and/or sampledensity and/or range of frequencies represented in the samples.Alternatively or additionally, the sampling determining device may beexplicitly indicated, e.g. by one or more parameters and/or indexesand/or pointers indicating and/or identifying and/or mapping thesampling determining device. It may be considered that samplinginformation indicates a frequency variation, e.g. coherence bandwidthand/or delay spread, in particular pertaining to measurements themeasurement report pertains to. It may be considered that samples aredetermined based on the frequency variation.

Transmitting sampling information may be targeted at a wirelessprecoding node, in particular at a wireless precoding node providingreference signaling, on which measurements may be performed, to whichsamples and/or the measurement report pertain. The measurement reportmay generally be based on and/or pertain to measuring or measurementperformed on signaling, in particular reference signaling. The referencesignaling may comprise cell-specific signaling and/or user-specificsignaling, e.g. CSI-RS (Channel State Information Reference Signaling)and/or DMRS (DeModulation-Reference Signaling).

The wireless device may be adapted for, and/or comprise a reportingmodule for, and/or the method for operating a wireless device maycomprise, preparing the measurement report, e.g. using and/or based onthe sampling determining device. Alternatively or additionally, it maybe considered that the wireless device may be adapted for, and/orcomprise a selecting module for, and/or the method for operating awireless device may comprise, selecting a sampling determining device,e.g. for preparing and/or for use in preparing a measurement report.Such selecting may comprise selecting out of a plurality of availableand/or pre-defined sampling determining devices and/or selectingparameters for the sampling determining device, e.g. upper and/or lowercut-off frequency/ies, and/or sampling density, etc. The samplingdetermining device may generally be selected based on a frequencyvariation of the measured signaling, in particular reference signaling.A frequency variation may generally be represented e.g. by a frequencydomain and/or time domain analysis and/or parametrization, e.g. by acoherence bandwidth (which may e.g. represent a frequency bandwidth overwhich the frequency varies little and/or remains essentially constant)and/or a delay-spread (which may be considered a time-domain measure offrequency variation). The variation may be evaluated over, and/orpertain to a given time interval, e.g. a measuring interval, and/or apre-defined time interval, which may e.g. a fraction or multitude of ameasuring interval.

Generally, the sample determining device may comprise a filter. Thesample determining device may be implemented in hardware and/orsoftware, in particular as a software filter, in particular in or forcontrol and/or radio circuitry. The sample determining device may beadapted to determine which samples are to be prepared in or for ameasurement report, and/or in which density (e.g., density in frequency)and/or which number of samples and/or over which range (e.g., infrequency), and/or which precision (e.g., number of bits) is providedand/or assigned for one or more samples, in particular for each sample.The sample determining device may in particular be implemented as a SINCfilter, especially a windowed SINC filter. It may be considered that thesample determining device (in particular a SINC filter/windowed SINCfilter) may be implemented to determine and/or define an upper limit forsamples, e.g. in frequency), in particular it may be implemented aslo-pass filter. The upper limit (cut-off) may be related and/or based ona determination of a high frequency range representing noise. The sampledetermining device may be implemented as a module, e.g. a softwaremodule. It may be considered that the sample determining device isgenerally adaptable. The wireless device may be adapted for, and/orcomprise an adaption module for, and/or the method for operating thewireless device may comprise, adapting the sample determining devicebased on a frequency variation or corresponding characteristic ofreceived reference signaling. The sample determining device may beadditionally or alternatively utilize transformation methods, e.g. basedon FFT (Fast Fourier Transform or equivalent) or other frequency (and/orassociated time domain) analyzing techniques, e.g. wavelet basedtransformation. Generally, the sample determining device may beconsidered to represent the approach and/or method and/or softwareand/or hardware used for determining samples. The samples determined mayrepresent the samples indicated and/or included in a measurement report.Samples may represent specific frequencies and/or frequency ranges(e.g., associated to corresponding taps) in a frequency range over whichmeasurements on signaling, in particular reference signaling, and/orassociated processing is performed (e.g., by the wireless device, whichmay comprise a measuring module for performing measurements and/ormeasuring). Each sample may represent or pertain to one or moreparameters associated to the frequency and/or frequency range, e.g.representing channel state information, and/or channel quality and/orreception power and/or signal quality (e.g., in terms of SIN, SINR orsimilar), and/or channel/precoder estimates, e.g. CQI and/or PMI and/orRI.

In some variants, the sampling information may be transmitted in ameasurement report, into which it may be included. A measurement reportmay comprise one or more messages transmitted, e.g., to a wirelessprecoding device or in uplink, if the precoding device or target of thereport is a network node. It may generally be considered that in thealternative, the sampling information indicating the sample determiningdevice is transmitted separately from the measurement report it pertainsto, e.g. in a summary report and/or dedicated control signaling.

The sample determining device may be adapted for, and/or determiningsamples may comprise, determining a sample density in frequency, and/ora number of samples for one or more frequency ranges. There may bedifferent sample densities for different frequency ranges covered by ameasurement report. For a given number of bits available for ameasurement report, the sample density (or number of samples) determineshow many bits are available for each sample, such that the resolution ofthe report (quality of information for each sample) is dependent on thedensity/number. Approaches described herein thus allow adapting theinformation quality.

Sampling information and/or a measurement report may pertain to one ormore different reference signalings, e.g. reference signaling utilisingdifferent precoders.

There is also considered a wireless precoding device for a Radio AccessNetwork. The wireless precoding device is adapted for transmittingsignaling based on precoding, the precoding being based on samplinginformation indicating a sample determining device used by a (another)wireless device for preparing a measurement report. The wirelessprecoding device may comprise a precoder or precoding module forprecoding and/or a transmitting module for transmitting signaling.

Moreover, a method for operating a wireless precoding device in a RadioAccess Network is proposed. The method comprises transmitting signalingbased on precoding, the precoding being based on sampling informationindicating a sample determining device used by another wireless devicefor preparing a measurement report.

The (other) wireless device may prepare and/or transmit the measurementreport, e.g. to the wireless precoding device. The measurement reportmay be received by the wireless precoding device.

The wireless precoding device may be adapted for, and/or comprise areference signaling module for, and/or the method for operating awireless precoding device may comprise, transmitting referencesignaling, e.g. to the wireless device. The measurement report and/orsampling information may pertain to the transmitted reference signaling.In some variants, the wireless precoding device may be adapted for,and/or comprise a (report) receiving module for, and/or the method foroperating a wireless precoding device may comprise, receiving ameasurement report, in particular a measurement report to which thesampling information pertains. The sampling information may be receivedwith, and/or be included in the measurement report.

Accordingly, the precoding device may adapt its transmission to thesample determining device, respectively its function, allowing improvedtransmission.

It may be considered that the precoding is additionally based on themeasurement report, in particular samples included therein and/or basedon channel/precoder information or channel state information includedtherein, e.g. CQI and/or PMI and/or RI.

Transmitting signaling based on precoding may be based on arepresentation of the sample determining device, for example anapproximation thereof, e.g. by interpolation or extrapolation. It may besufficient to approximate the sample determining device withoutrepresenting it exactly to improve precoding and/or determine animproved precoder. The representation may for example correspond to anassumption of the sampling determining device used, and/or of afrequency range acceptable based on the sampling information. Generally,transmitting signaling based on precoding may be based on and/or utilisea frequency limitation or selection device, which may be based on therepresentation. Such a frequency limitation or selection device may inparticular comprise a filter like an interpolation filter and/orwindowed filter, and/or a frequency raking device. The frequencylimitation or selection device may be adapted or selected or calculatedor determined based on the representation of the sample determiningdevice, e.g. to match or essentially/approximately match its frequencybehaviour, in particular regarding high frequencies (high in particularin relation to an upper cutoff frequency). The frequency limitation orselection device may for example be based on and/or represent a SINC orwindowed SINC, in particular if the sample determining device representssuch. Generally, a frequency limitation and/or selection device may beimplemented in software and/or hardware, in particular in or for controland/or radio circuitry. In general, a frequency limitation or selectiondevice may be frequency and/or time selective, in particular frequencyand time selective, e.g. limiting transmission in frequency and/or time.

There may also be considered a program product comprising instructionsadapted for causing control circuitry to control and/or perform any oneof the methods described herein.

A carrier medium is disclosed, the carrier medium carrying and/orstoring a program product as described herein, and/or instructionsadapted for causing control circuitry to control and/or perform any oneof the methods described herein.

Also, there may be considered a wireless communication system comprisinga wireless device as described herein, and/or a wireless precodingdevice as described herein. In particular, the wireless device may be aterminal and the wireless precoding device may be a network node, orvice versa.

A wireless precoding device may be any device adapted for precoding. Awireless precoding device may comprise and/or be connected orconnectable, e.g. to utilise for transmitting based on precoding, amulti-antenna array. A wireless precoding device may in particular beimplemented as network node, e.g. a radio node and/or base station.However, a terminal utilising a multi-antenna array and/or precoding mayalso be considered representing a wireless precoding device.

A wireless device may be any device adapted to provide a measurementreport and/or corresponding sampling information as described herein. Inparticular, a terminal may be considered a wireless device. However, anetwork node performing similar measurements and/or providing ameasurement report may also be considered a wireless device. The term“wireless” herein indicates a mode of signaling or transmitting, namelywireless and/or over an air interface and/or using radiowaves/frequencies.

Preparing a measurement report may comprise providing and/or determiningand/or collecting and/or processing and/or formatting information toconstruct a measurement report. Preparing may comprise constructing thereport, and/or inserting the related information into the report.Preparing may be based on measurement performed and/or measuring. It maybe considered that preparing a measurement report is part of a CSIprocess.

The sampling determining device may in particular be used for preparinga measurement report. It may be considered that the device, or a devicebased on it, may be used for handling and/or receiving other kinds ofsignaling, e.g. data signaling (signaling pertaining to data other thanreference signaling). However, it may be considered that, since thewireless precoding device, when receiving the sampling information, mayadapt its precoding and/or transmission accordingly, no use for asampling determining device is necessary unless indicated when preparingmeasurement reports.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided to illustrate concepts and approachesdescribed herein, and are not intended to limit their scope. Thedrawings comprise:

FIG. 1, showing an exemplary wireless device procedure for a coherencebandwidth adaptive CSI-report;

FIG. 2, showing an exemplary transmitter procedure for frequencyselective pre-coding using interpolation filter;

FIG. 3, showing an overview of coherence bandwidth CSI procedure;

FIG. 4, showing an exemplary wireless device;

FIG. 5, showing an exemplary wireless precoding device;

FIG. 6, showing a flow diagram of an exemplary method for operating awireless device;

FIG. 7, showing an exemplary wireless device;

FIG. 8, showing a flow diagram of an exemplary method for operating awireless precoding device; and

FIG. 9, showing an exemplary wireless precoding device.

DETAILED DESCRIPTION

In the following, by way of example, it is referred to a transmitter anda receiver. The transmitter may be considered to represent a wirelessprecoding device, whereas the receiver may be considered to represent awireless device. In specific examples, the transmitter may be a networknode (e.g., eNodeB), the receiver a terminal. However, as outlinedabove, the roles may be reversed, e.g. if a terminal is adapted forprecoding. Indeed, both devices may be able to take both roles, insimilar process, depending on which device prepares the measurementreport and which device uses precoding at a given point in time and/orfor specific transmissions.

There is proposed an approach related to measurement reporting. Theapproach uses the underlying structure of the estimation problem. Thisstructure is that the transmitter in its pre-coder selection algorithmswill use knowledge about the properties of at least the frequency andtime domain properties of the radio channel for the estimation. In thecurrent state of the art solutions this information that the UE has istypically lost. But it is in fact very valuable and if one can in thereporting include this information and also pick a matching time andfrequency domain sampling in the CSI reporting, this approach will tendto optimal CSI reporting. Accordingly, suitable sampling information maybe provided.

Generally, there may be considered a method for communicating channelstate information from a wireless device, and/or a correspondinglyadapted wireless device. The channel state information may e.g. comprisesampling information and/or a measurement report. The method maycomprise, and/or the wireless device may be adapted for, and/or comprisea receiving module for, receiving a (e.g., downlink or reverse link)reference signal, or generally for receiving reference signaling. Themethod may optionally comprise, and/or the wireless device may beadapted for, and/or comprise a variation determining module for,performing a determination of, e.g. a measurement and/or analysis and/orcalculation and/or estimation of, frequency variation of and/orpertaining to the reference signal, e.g. a coherence bandwidth (and/ordelay-spread).

The wireless device may be adapted for, and/or comprise an estimatingmodule for, and/or the method may comprise generating channel and/orpre-coder estimates with a frequency density according to frequencyvariation, e.g. a coherence estimate as determined. This may beconsidered a variant of preparing a measurement report. Using thefrequency density may be considered to represent using a sampledetermining device, e.g. to select the frequency density, which may beconsidered to determine the samples in frequency space used for themeasurement report respectively its preparation. The method foroperating the wireless device may include, and/or the wireless devicemay be adapted for, and/or comprise a transmitting module for,transmitting one or more measurement reports, e.g. CSI reports, whichmay include sampling information, e.g. information about the coherencebandwidth and/or delay-spread, and/or channel/pre-coder information,e.g. CQI and/or PMI.

There may be considered a wireless device for performing pre-coding(which may be considered a wireless precoding device), respectively amethod for operating such. The wireless precoding device may be adaptedfor, and/or comprise a receiving module for, and/or the method maycomprise, receiving a measurement report, e.g. a CSI-report, which mayinclude channel state information, e.g. channel/pre-coder estimates,e.g. CQI and/or PMI, and/or receiving sampling information, e.g. in themeasurement report or separate therefrom. The sampling information mayindicate e.g. (implicitly or explicitly) coherence bandwidth (and/ordelay-spread) properties, e.g. of samples and/or used for determiningsamples in the report. Thus, the sampling information may be consideredrepresentative for the sampling determining device used for preparingthe measurement report. The method may comprise, and/or the wirelessdevice maybe adapted for, and/or comprise a frequency limiting modulefor, determining a frequency limitation or selection device, e.g. bygenerating an interpolation filter (representing the device) based uponsaid sampling information, e.g. coherence bandwidth properties. It maybe considered that the wireless precoding device may be adapted for,and/or comprise a precoding module for, and/or the method may comprisedetermining one or more precoders (as a form of precoding, not thatdetermining the frequency limitation or selection device may beimplemented as part of precoding), e.g. by calculating one or moreprecoders, e.g. frequency/time selective pre-coders, based on thefrequency limitation or selection device, e.g. the interpolating filter,and/or the channel state information and/or measurement report, inparticular channel/precoder estimates. The method may further comprise,and/or the wireless precoding device may be adapted for, and/or comprisea transmitting module for, transmitting signaling, e.g. data or datasignaling, using the determined precoder/s.

The proposed approaches facilitate

-   -   Reduced control channel load as fewer precoders are reported        when coherence bandwidth is large (e.g. LOS case).    -   Improved performance in the CSI reporting and hence precoder        selection as more precoders may be reported if the channel is        frequency selective.    -   Improved performance in the channel estimation step in the        actual transmission as interpolation across larger bandwidth is        enabled if precoders are applied with smooth transitions        according to the new information available in the precoder        selection algorithms at the precoding device respectively on the        network side.

The following variants may be implemented individually, or incombination.

In a variant, the frequency variation or coherence of the channel(respectively, the reference signaling, which are transmitted on thechannel that is estimated) may be estimated as the delay spread of thechannel. It may be generally considered that in a variant the frequencyvariation or coherence may be determined as, and/or based, on aselection among a plurality of pre-determined frequency filters. Inanother variant, the frequency variation or coherence may be determinedas, and/or based on, a selection among a plurality of pre-determinedtime-domain filters.

In a further variant, the frequency limitation or selection device, inparticular an interpolation filter, may be selected among a plurality offrequency domain filters. It may be considered, that in a variant, thefrequency limitation or selection device, e.g. an interpolation filter,is represented by zero-padding of a missing part of a time domainresponse. In another variant, the frequency limitation or selectiondevice, e.g. an interpolation filter, may be determined to bezero-order-hold across the interpolation points. In other variants, ahigher-order interpolation may be utilised. The sampling information mayindicate whether a zero-order-hold is to be used, e.g. if channelconditions and/or interference conditions (transmission conditions) arepoor, and/or the wireless device has poor reception capabilities.

It may be considered that, in a variant, the measurement report, e.g. aCSI-report, contains information, e.g. in a header, indicating a numberof channel/pre-coding samples in said CSI-report, which implicitlyindicate the sample determining device, e.g. the filter used may beimplicitly determined based on the number of samples. In some variantthereof, the number of samples in the report may be signaled separatelyfrom the samples or the report itself.

It may be considered that the size of a measurement/CSI report is fixed(e.g., predetermined, for example by a standard). The information aboutthe number of samples in this case may also determine the quantizationof the channel/pre-coder samples (e.g., the number of bits availabletherefor). In a variant, the quantization may be defined as the numberof bits per antenna for the channel vectors. A variant is disclosed inwhich the quantization pertains to and/or is based on a plurality ofcode-books, wherein the number of entries of a code-book may scale withthe resolution in the quantization. In a variant, the interpolationfilter may represent a SINC function, in a specific variant the filtermay represent a windowed SINC function. Generally, in there may beconsidered that the interpolation (for the corresponding filter) isbased on a minimization problem using an FFT, wherein the filter settingmay be the number of non-zero values to optimize over in the saidminimization problem. This implies that the placement of a fixed numberof taps in the time domain can be found to minimize the error comparedto the signaled frequency information in the measurement or CSI report.

There may be considered a variant in which the number of samples (e.g.,representing the number of reported precoding samples) is determinedbased on the measured channel characteristics and a threshold. Thethreshold may be dynamically signaled by the network, configured by anetwork node or a wireless precoding device, or fixed in specifications.

The maximum interpolation bandwidth of the channel estimator filters ina variant may be determined based on previously reported channel stateinformation (e.g., CSI, e.g. CQI and PMI), and/or precoding/CSIinformation.

When performing an estimate on the receiver side (in this example, theterminal or UE side), the UE needs to estimate the coherence bandwidth(delay spread) of the channel and an estimate of the SINR. These twoparameters are used to calculate an “estimated optimal” filter. Thisfilter is wide in frequency domain (short in time domain) if thecoherence bandwidth is wide. The filter is also made wider if theestimated SINR is low due to that you want to gain processing gain bymaking the filter wider.

The filter (representing a sample determining device) acts as a low-passfilter hence will limit the frequency content in the channel estimate.This implies that according to Nyquist's theorem, fewer samples areneeded in frequency domain if the filter is a SINC function (infrequency domain), while maintaining perfect reconstruction on thetransmitter side (e.g., network side) using the SINC function. The sameshould hold true (i.e. errors below quantization noise) as a suitablefilter is chosen. One candidate is some type of windowed SINC function,pertaining to which it is known that the error term goes to zero whenthe filter length goes to infinite.

If the receiver/UE reports pre-coders (e.g., a CSI/PMI information), thesame holds true for beam-forming wide-band type pre-coders (i.e.pre-coders optimizing the signal from the UE without consideration tointerference from other UEs).

One implementation of the concept as shown in FIG. 1 may comprise amethod for communicating channel state information from a wirelessdevice, including receiving a (e.g., reverse link or downlink) referencesignal; performing a measurement (e.g. frequency variation likecoherence bandwidth or delay-spread) estimate on the said referencesignal; generating channel and/or pre-coder estimates with a frequencydensity according to the said measurement; transmitting CSI reportsincluding information about at least of both said coherence andchannel/pre-coder information.

Another implementation of the concept as shown in FIG. 2 may comprise awireless (precoding) device adapted for, and/or a method comprisingperforming pre-coding including the steps of receiving a CSI-reportincluding channel/pre-coder estimates; receiving a CSI-report includingcoherence bandwidth (or delay-spread) properties (e.g. as may beinferred from the number of reported precoder estimates); generating aninterpolation filter based upon said coherence bandwidth properties; andcalculating a frequency/time selective pre-coders from said estimatesand said interpolation filter.

FIG. 3 shows an overview of an exemplary CSI procedure, with atransmitter performing as indicated with reference to FIG. 2 interactingwith a receiver (wireless device) as indicated with reference to FIG. 1.

The approaches described herein facilitate better and frequencyselective precoding. Using frequency selective pre-coding at thetransmitter has the advantage, that the effective channel becomessmother and much easier to estimate at the receiver, which impliespotentially much higher performance enabled by better utilization of alarge antenna array. There is also the added benefit of reducing controlchannel load (overhead).

FIG. 4 schematically shows a wireless device 10, which may be consideredan example for a receiver or wireless device as described herein.Wireless device 10 comprises control circuitry 20, which may comprise acontroller connected to a memory. Any module of the wireless device,e.g. receiving module and/or transmitting module and/or sampledetermining device may be implemented in and/or executable by, thecontrol circuitry 20, in particular as module in the controller.Wireless device 10 also comprises radio circuitry 22 providing receivingand transmitting or transceiving functionality, the radio circuitry 22connected or connectable to the control circuitry. An antenna circuitry24 of the terminal 10 is connected or connectable to the radio circuitry22 to collect or send and/or amplify signals. Radio circuitry 22 and thecontrol circuitry 20 controlling it are configured for cellularcommunication with a network. The wireless device 10 may be adapted tocarry out any of the methods for operating a wireless device disclosedherein; in particular, it may comprise corresponding circuitry, e.g.control circuitry.

FIG. 5 schematically show a wireless precoding device 100, like anetwork node or base station, which in particular may be an eNodeB orsimilar for NR. Wireless precoding device 100 comprises controlcircuitry 120, which may comprise a controller connected to a memory.Any module, e.g. receiving module and/or transmitting module and/orconfiguring module of the wireless precoding device may be implementedin and/or executable by the control circuitry 120. The control circuitryis connected to control radio circuitry 122 of the network node 100,which provides receiver and transmitter and/or transceiverfunctionality. An antenna circuitry 124 may be connected or connectableto radio circuitry 122 for signal reception or transmittance and/oramplification. The wireless precoding device 100 may be adapted to carryout any of the methods for operating a network node disclosed herein; inparticular, it may comprise corresponding circuitry, e.g. controlcircuitry. The antenna circuitry may be connected to and/or comprise anantenna array. The wireless precoding device 100, respectively itscircuitry, may be adapted to perform precoding. In particular, theantenna circuitry may comprise and/or be connected or connectable to amulti-antenna array.

FIG. 6 shows a flow diagram indicating an algorithm for a method foroperating a wireless device as described herein. The method may comprisean action TS10 of transmitting sampling information indicating a sampledetermining device used by the wireless device (10) for preparing ameasurement report. The method optionally may comprise an action TS08 ofpreparing a measurement report.

FIG. 7 shows a wireless device for a RAN, e.g. a wireless device asdescribed herein. The wireless device comprises a module TM10 forperforming action TS10. Optionally, it may comprise a module TM08 forperforming action TS08.

FIG. 8 shows a flow diagram indicating an algorithm for a method foroperating a wireless precoding device as described herein. The methodmay comprise an action NS10 of transmitting signaling based onprecoding, the precoding being based on sampling information indicatinga sample determining device used by another wireless device forpreparing a measurement report. The method may comprise an optional stepNS08 of receiving the sampling information and/or the measurementreport.

FIG. 9 shows an exemplary network node for a RAN, e.g. a network node asdescribed herein. The network node comprises a module NM10 forperforming action NS10. Optionally, it may comprise a module NM08 forperforming action NS08.

Some useful abbreviations comprise:

3GPP Third Generation Partnership Project

eNB Enhanced NodeB

CQI Channel-Quality Indicator

CRS Cell-Specific Reference Symbol

CSI Channel-State Information

CSI-IM CSI Interference Measurement

CSI-RS CSI Reference Symbol

DCI Downlink Control Information

HARQ Hybrid Automatic Repeat-reQuest

LTE Long Term Evolution

MAC Medium Access Control

MCS Modulation and Coding Scheme

MI Mutual Information

MIMO Multiple Input Multiple Output

NDI New Data Indicator

(e)PDCCH (enhanced) Physical Downlink Control Channel

PDU Protocol Data Unit

PMI Pre-coding Matrix Indicator

PRB Physical Resource Block

RAN Radio Access Network

RI Rank Indicator

RV Redundancy Version

RRC Radio Resource Control

TM Transmission Mode

TTI Transmission Time Interval

UE User Equipment

There is also considered a program product comprising instructionsadapted for causing control circuitry to carry out and/or control anymethod described herein, in particular when executed on the controlcircuitry.

A carrier or storage medium is also described, the storage mediumstoring a program product as described herein, and/or instructionsadapted for causing control circuitry to carry out and/or control anymethod described, in particular when executed on the control circuitry.

A Radio Access Network (RAN) may be any kind of cellular and/or wirelessradio network, which may be connected or connectable to a core network.The approaches described herein are particularly suitable for a 5Gnetwork, e.g. advance LTE and/or NR (New Radio), respectively successorsthereof. A RAN may comprise one or more network nodes. A network nodemay in particular be a radio node adapted for radio and/or wirelessand/or cellular communication with one or more terminals. A terminal maybe any device adapted for radio and/or wireless and/or cellularcommunication with or within a RAN, e.g. a user equipment (UE) or mobilephone or smartphone or computing device or vehicular communicationdevice or device for machine-type-communication (MTC), etc. A terminalmay be mobile, or in some cases stationary. Transmitting in downlink maypertain to transmission from the network or network node to theterminal. Transmitting in uplink may pertain to transmission from theterminal to the network or network node.

Signaling may generally comprise one or more signals and/or one or moresymbols. Reference signaling may comprise one or more reference signalsor symbols. Reference signaling may be cell-specific or user-specific. Aterminal or network node may be adapted to measure reference signaling,e.g. for demodulation and/or power control and/or to determine channelstate information representing the transmission quality of a measuredchannel (representing the propagation of signaling using specifictransmission parameters and/or the transmission path). Referencesignaling may in particular be CSI-RS (Channel State InformationReference Signaling). It may be considered that reference signaling isreceived by the terminal.

A measurement report may generally represent information based on,and/or pertaining to, measurement/s that have been performed onreference signaling. The report type may pertain to the measurementreport. A measurement report may comprise and/or indicate measurementsamples and/or information pertaining thereto and/or parametersdetermined based on measurements performed, and/or information relatedto channel state or quality, e.g. CQI and/or PMI and/or RI. The reportmay contain values computed and/or estimated and/or calculated based onmeasurement results, as examples of a report being based on and/ordetermined based on measurements.

There is disclosed a carrier (or storage) medium arrangement carryingand/or storing at least any one of the program products described hereinand/or code executable by control circuitry, the code causing thecontrol circuitry to perform and/or control at least any one of themethods described herein. A carrier medium arrangement may comprise oneor more carrier media. Generally, a carrier medium may be accessibleand/or readable and/or receivable by control circuitry. Storing dataand/or a program product and/or code may be seen as part of carryingdata and/or a program product and/or code. A carrier medium generallymay comprise a guiding/transporting medium and/or a storage medium. Aguiding/transporting medium may be adapted to carry and/or carry and/orstore signals, in particular electromagnetic signals and/or electricalsignals and/or magnetic signals and/or optical signals. A carriermedium, in particular a guiding/transporting medium, may be adapted toguide such signals to carry them. A carrier medium, in particular aguiding/transporting medium, may comprise the electromagnetic field,e.g. radio waves or microwaves, and/or optically transmissive material,e.g. glass fiber, and/or cable. A storage medium may comprise at leastone of a memory, which may be volatile or non-volatile, a buffer, acache, an optical disc, magnetic memory, flash memory, etc.

A terminal may be implemented as a user equipment. A terminal or a userequipment (UE) may generally be a device configured for wirelessdevice-to-device communication and/or a terminal for a wireless and/orcellular network, in particular a mobile terminal, for example a mobilephone, smart phone, tablet, PDA, etc. A user equipment or terminal maybe a node of or for a wireless communication network as describedherein, e.g. if it takes over some control and/or relay functionalityfor another terminal or node. It may be envisioned that terminal or auser equipment is adapted for one or more RATs, in particularLTE/E-UTRA. A terminal or user equipment may generally be proximityservices (ProSe) enabled, which may mean it is D2D capable or enabled.It may be considered that a terminal or user equipment comprises radiocircuitry and/control circuitry for wireless communication. Radiocircuitry may comprise for example a receiver device and/or transmitterdevice and/or transceiver device. Control circuitry may include one ormore controllers, which may comprise a microprocessor and/ormicrocontroller and/or FPGA (Field-Programmable Gate Array) deviceand/or ASIC (Application Specific Integrated Circuit) device. It may beconsidered that control circuitry comprises or may be connected orconnectable to memory, which may be adapted to be accessible for readingand/or writing by the controller and/or control circuitry. It may beconsidered that a terminal or user equipment is configured to be aterminal or user equipment adapted for LTE/E-UTRAN. Reference signalingin the uplink may be associated to a terminal, e.g. SRS.

A radio node or network node or base station may be any kind of radionode or base station of a wireless and/or cellular network adapted toserve one or more terminals or user equipments. It may be consideredthat a base station is a node or network node of a wirelesscommunication network. A radio node or network node or base station maybe adapted to provide and/or define and/or to serve one or more cells ofthe network and/or to allocate frequency and/or time resources forcommunication to one or more nodes or terminals of a network. Generally,any node adapted to provide such functionality may be considered a basestation. It may be considered that a base station or more generally anetwork node, in particular a radio network node, comprises radiocircuitry and/or control circuitry for wireless communication. It may beenvisioned that a base station or radio node is adapted for one or moreRATs, in particular LTE/E-UTRA. Radio circuitry may comprise for examplea receiver device and/or transmitter device and/or transceiver device.Control circuitry may include one or more controllers, which maycomprise a microprocessor and/or microcontroller and/or FPGA(Field-Programmable Gate Array) device and/or ASIC (Application SpecificIntegrated Circuit) device. It may be considered that control circuitrycomprises or may be connected or connectable to memory, which may beadapted to be accessible for reading and/or writing by the controllerand/or control circuitry. A base station may be arranged to be a node ofa wireless communication network, in particular configured for and/or toenable and/or to facilitate and/or to participate in cellularcommunication, e.g. as a device directly involved or as an auxiliaryand/or coordinating node. Generally, a base station may be arranged tocommunicate with a core network and/or to provide services and/orcontrol to one or more user equipments and/or to relay and/or transportcommunications and/or data between one or more user equipments and acore network and/or another base station and/or be Proximity Serviceenabled.

An eNodeB (eNB) may be envisioned as an example of a network node orradio node or base station, e.g. according to an LTE standard. A radionode or base station may generally be proximity service enabled and/orto provide corresponding services. It may be considered that a radionode base station is configured as or connected or connectable to anEvolved Packet Core (EPC) and/or to provide and/or connect tocorresponding functionality. The functionality and/or multiple differentfunctions of a radio node or base station may be distributed over one ormore different devices and/or physical locations and/or nodes. A radionode or base station may be considered to be a node of a wirelesscommunication network. Generally, a radio node or base station may beconsidered to be configured to be a coordinating node and/or to allocateresources in particular for cellular communication between two nodes orterminals of a wireless communication network, in particular two userequipments.

Beamformed transmission of signaling may comprise beamforming totransmit a beam pattern. Beamforming may be based on a precoder. Aprecoder may represent a beamforming configuration, in particular amapping for a signal to a plurality of antenna elements, in particularfor beamforming and/or MIMO operation. It may be considered that aprecoder is represented by a matrix and/or comprises weights forcontrolling different antenna elements of a subarray for beamforming. Aprecoder, in particular a first or second precoder (e.g., of a firstiteration described herein) may be associated to a codebook. A codebookmay comprise a plurality of precoders associated to allowed beamformingconfigurations, e.g. based on a standard like LTE and/or operatingconditions, based on which a standard-defined codebook for example maybe limited. When beamforming, a desired signaling is provided by theoverlay of the radiation patterns transmitted by the antenna elements ofthe subarray used for beamforming according to the precoder used. Aprecoder may generally be associated to and/or pertain to and/or addressa subarray of antenna elements used for beamforming to provide thedesired signaling (respectively port). Generally, a precoder may pertainto one or more, in particular two or more, (physical) antenna elements,which may be intended for use in transmission (e.g., provided withnon-zero signal amplitude for transmission).

Precoding may comprise determining a precoder and/or providing aprecoder for transmitting. Transmitting based on precoding and/or aprecoder may comprise using the precoder/precoding to transmit, e.g. bycontrolling radio and/or antenna circuitry according to the precodingand/or precoder.

Signaling may comprise one or more signals and/or symbols, e.g. one ormore reference signals or symbols like CSI-RS. A beam pattern (inparticular, an angular and/or spatial distribution and/or fieldstructure) may be associated to a port. An angular distribution may berepresented by a two-dimensional/plane representation and/or athree-dimensional distribution, e.g. pertaining to a spatial or solidangle. Signaling may be associated to a part of the beam pattern. A beampattern may in particular comprise a main lobe of radiation. Symbols orsignals of signaling (respectively a port) may be defined to allowestimation of the associated channel by a receiver, e.g. a terminal likea UE. Estimation of a channel may comprise measurements of thesignaling, in particular reference signals associated to the channeland/or port. Such measurements may comprise measurements related toamplitude and/or phase and/or frequency and/or duration and/orSignal-to-Noise (e.g., SINR, SIR and/or SNR). Different subarrays of anantenna array may differ in at least one antenna element.

Performing measurements may include measuring signaling, and/orperforming processing based thereon, e.g. filtering, averaging,integrating, normalizing, scaling, weighting, determining and/orextracting and/or providing samples, etc. The latter may be based on,and/or performed by, a sample determining device, and/or be performedduring measuring, or after, and/or while or before preparing ameasurement report.

Obtaining and/or determining a precoder may comprise any form ofacquiring information indicating the precoder, e.g. reading from amemory, receiving data indicating the precoder, and/or determining theprecoder, e.g. based on received data like a measurement report.

Reference signaling may comprise one or more reference signals orsymbols. Reference signals may be adapted or intended for a receiver(e.g., a terminal) to perform measurements on and/or to provide ameasurement report on. Reference signals may be defined by a standard,e.g. CSI-RS defined by 3GPP standards, e.g. LTE or NR. Measurementreporting and/or providing a measurement report may generally comprisetransmitting a measurement report, in particular to a source/transmitterof reference signaling, e.g. a network node, and/or performingmeasurements, e.g. on reference signaling, and/or evaluatingmeasurements (e.g., processing the measurement results). A measurementreport may be based on the performed measurements and/or the evaluating.Generally, reference signaling may be cell-specific orterminal-specific. CSI-RS may be considered an example forterminal-specific or user-specific reference signaling.

Configuring (e.g., with or for a configuration) a device like a terminalor network node may comprise bringing the device into a state inaccordance with the configuration. A device may generally configureitself, e.g. by adapting a configuration. Configuring a terminal, e.g.by a network node, may comprise transmitting a configuration orconfiguration data indicating a configuration to the terminal, and/orinstructing the terminal, e.g. via transmission of configuration data,to adapt the configuration configured.

A configuration may in particular pertain to measurement reporting, e.g.to a CSI process. Measurement reporting may generally pertain tospecific signaling (or an associated port), which may be indicated orconfigured to the terminal by the network or network node, e.g. bytransmitting corresponding configuration data. Measurement reporting maygenerally indicate a preferred port or port combination (or precoder orprecoder combination) to be used, which may be referred to as port orprecoder selection.

A CSI process may generally comprise receiving, from a network node,reference signaling (CSI-RS), and providing a measurement report basedon the received reference signaling. The measurement report may inparticular indicate or comprise CSI information, in particular CQI(Channel Quality Information), PMI (Precoding Matrix Indicator) and/orRI (Rank Indicator).

In this disclosure, for purposes of explanation and not limitation,specific details are set forth (such as particular network functions,processes and signaling steps) in order to provide a thoroughunderstanding of the technique presented herein. It will be apparent toone skilled in the art that the present concepts and aspects may bepracticed in other embodiments and variants that depart from thesespecific details.

For example, the concepts and variants are partially described in thecontext of Long Term Evolution (LTE) or LTE-Advanced (LTE-A) or NextRadio mobile or wireless communications technologies; however, this doesnot rule out the use of the present concepts and aspects in connectionwith additional or alternative mobile communication technologies such asthe Global System for Mobile Communications (GSM). While the followingembodiments will partially be described with respect to certainTechnical Specifications (TSs) of the Third Generation PartnershipProject (3GPP), it will be appreciated that the present concepts andaspects could also be realized in connection with different PerformanceManagement (PM) specifications.

Moreover, those skilled in the art will appreciate that the services,functions and steps explained herein may be implemented using softwarefunctioning in conjunction with a programmed microprocessor, or using anApplication Specific Integrated Circuit (ASIC), a Digital SignalProcessor (DSP), a Field Programmable Gate Array (FPGA) or generalpurpose computer. It will also be appreciated that while the embodimentsdescribed herein are elucidated in the context of methods and devices,the concepts and aspects presented herein may also be embodied in aprogram product as well as in a system comprising control circuitry,e.g. a computer processor and a memory coupled to the processor, whereinthe memory is encoded with one or more programs or program products thatexecute the services, functions and steps disclosed herein.

It is believed that the advantages of the aspects and variants presentedherein will be fully understood from the foregoing description, and itwill be apparent that various changes may be made in the form,constructions and arrangement of the exemplary aspects thereof withoutdeparting from the scope of the concepts and aspects described herein orwithout sacrificing all of its advantageous effects. The aspectspresented herein can be varied in many ways.

The invention claimed is:
 1. A wireless device for a Radio AccessNetwork, the wireless device comprising: a sample determining deviceconfigured to: determine sampling information including at least afrequency variation to a reference signal of a radio channel used forchannel estimation and a sample density in at least one of frequency andtime properties of the radio channel used for channel estimation, thesample density being based at least on the frequency variation, thefrequency variation being at least one of a coherence bandwidth and adelay spread; prepare a measurement report including at least thesampling information and the sample determining device used by thewireless device for preparing the measurement report; and the wirelessdevice being configured to: transmit at least the measurement report. 2.The wireless device according to claim 1, wherein the sample determiningdevice comprises a filter.
 3. A method for operating a wireless devicein a Radio Access Network, the wireless device comprising a sampledetermining device, the method comprising: determining samplinginformation including at least a frequency variation to a referencesignal of a radio channel used for channel estimation and a sampledensity in at least one of frequency and time properties of the radiochannel used for channel estimation, the sample density being based atleast on the frequency variation, the frequency variation being at leastone of a coherence bandwidth and a delay spread; preparing a measurementreport including at least the sampling information and the sampledetermining device used by the wireless device for preparing themeasurement report; and transmitting at least the measurement report. 4.The method according to claim 3, wherein the sample determining devicecomprises a filter.
 5. A wireless precoding device for a Radio AccessNetwork, the Radio Access Network supporting communication with at leasta wireless device, the wireless precoding device being configured to:receive at least a measurement report including at least samplinginformation and a sample determining device used by the wireless devicefor preparing the measurement report, the sampling information includingat least a frequency variation to a reference signal of a radio channelused for channel estimation and a sample density in at least one offrequency and time properties of the radio channel used for channelestimation, the sample density being based at least on the frequencyvariation, the frequency variation being at least one of a coherencebandwidth and a delay spread; and transmit signaling based on precoding,the precoding being based on the sampling information and the sampledetermining device used at least by the wireless device for preparing ameasurement report.
 6. The wireless precoding device according to claim5, wherein transmitting signaling based on precoding is based on arepresentation of the sample determining device.
 7. A method foroperating a wireless precoding device in a Radio Access Network, theRadio Access Network supporting communication with at least a wirelessdevice, the method comprising: receiving at least a measurement reportincluding at least sampling information and a sample determining deviceused by the wireless device for preparing the measurement report, thesampling information including at least a frequency variation to areference signal of a radio channel used for channel estimation and asample density in at least one of frequency and time properties of theradio channel used for channel estimation, the sample density beingbased at least on the frequency variation, the frequency variation beingat least one of a coherence bandwidth and a delay spread; andtransmitting signaling based on precoding, the precoding being based onthe sampling information and the sample determining device used at leastby the wireless device for preparing a measurement report.
 8. The methodaccording to claim 7, wherein transmitting signaling based on precodingis based on a representation of the sample determining device.
 9. Acomputer storage medium storing an executable computer programcomprising instructions that when executed cause control circuitry to atleast one of control and perform a method for operating a wirelessdevice in a Radio Access Network, the wireless device comprising asample determining device, the method comprising: determining samplinginformation including at least a frequency variation to a referencesignal of a radio channel used for channel estimation and a sampledensity in at least one of frequency and time properties of the radiochannel used for channel estimation, the sample density being based atleast on the frequency variation, the frequency variation being at leastone of a coherence bandwidth and a delay spread; preparing a measurementreport including at least the sampling information and the sampledetermining device used by the wireless device for preparing themeasurement report; and transmitting at least the measurement report.10. A wireless communication system comprising a wireless device for aRadio Access Network and a wireless precoding device for the RadioAccess Network, the wireless device comprising: a sample determiningdevice configured to: determine sampling information including at leasta frequency variation to a reference signal of a radio channel used forchannel estimation and a sample density in at least one of frequency andtime properties of the radio channel used for channel estimation, thesample density being based at least on the frequency variation, thefrequency variation being at least one of a coherence bandwidth and adelay spread; prepare a measurement report including at least thesampling information and the sample determining device used by thewireless device for preparing the measurement report; and the wirelessdevice being configured to: transmit at least the measurement report;and the wireless precoding device being configured to: receive at leastthe measurement report including at least the sampling information andthe sample determining device used by the wireless device for preparingthe measurement report, the sampling information including at least thefrequency variation to the reference signal of the radio channel usedfor channel estimation and the sample density in at least one offrequency and time properties of the radio channel used for channelestimation, the sample density being based at least on the frequencyvariation; and transmit signaling based on precoding, the precodingbeing based on the sampling information and the sample determiningdevice used at least by the wireless device for preparing themeasurement report.
 11. The wireless communication system according toclaim 10, wherein the sample determining device comprises a filter.